<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
</head>
<body>

<div id="app">
    <h2 :style="getStyles()">{{message}}</h2>
</div>

<script src="../js/vue.js"></script>
<script>
    const app = new Vue({
        el: '#app',
        data: {
            message: 'hi',
            fontSize: '100px',
            bgColor: 'red',
        },
        methods: {
            getStyles: function () {
                return {'font-size': this.fontSize, 'background-color': this.bgColor};
            }
        }
    })
</script>

</body>
</html>